(1) Field of the Invention
The present invention relates to methods used to fabricate semiconductor devices, and more specifically to a method used suppress the effect of floating body regions used with metal oxide semiconductor field effect transistor (MOSFET) devices formed on an SOI layer.
(2) Description of Prior or Art
The ability to form MOSFET devices, such as a partially depleted MOSFET device, on a silicon on insulator (SOI) layer has resulted in decreased junction capacitance and thus increased device performance. To avoid a body floating phenomena which can result in deleterious device characteristics such as a low source to drain breakdown voltage, as well as threshold voltage reduction, direct contact between the semiconductor substrate and a body contact region, formed in the SOI layer, is employed. However designs using a body contact region of a first conductivity type can form unwanted parasitic transistor with source and drain regions of a second conductivity type, in an area adjacent to, or underlying the gate structure of the MOSFET device. The leakage current resulting from the unwanted parasitic transistors can negatively influence the performance of the MOSFET device.
The present invention will describe a structure, as well as a process used to fabricate this structure, that reduces the leakage current driven by the parasitic transistors that can form at a gate electrode junction. The same structure in addition to reducing leakage current of unwanted parasitic transistors, also allows greater control of gate width to be realized. Prior art such as Kroell et al in U.S. Pat. No. 6,537,861 B1, Beyer et al in U.S. Pat. No. 5,405,795, Kim et al in U.S. Pat. No. 6,521,959 B2, and Tyson et al in U.S. Pat. No. 5,145,802, describe methods of forming body extension and body contact regions, however these prior art do not describe the structure and process used in this present invention which features the reduction of the deleterious leakage current generated by the presence of the body contact region via inclusion of novel isolation regions.